【程式設計師面試演算法】求陣列的最大子序列和，9種程式語言實現！建議收藏

演算法：給你一個整數陣列 nums（至少包含一個元素），請你找出一個具有最大和的連續子陣列（至少包含一個元素），返回其最大和。

本文用 c、c++、python、java、kotlin、swift、js、rust、go 9種主流程式語言實現。基於貪心演算法實現。

演算法原理：遍歷陣列，並計算包含當前元素的子序列和，若當前元素之前的序列和小於0，則丟棄當前元素之前的數列。

C

#include <stdio.h>

int maxSubArray(int* nums, int numsSize) {
    int max_sum = nums[0];
    int current_sum = nums[0];

    for (int i = 1; i < numsSize; i++) {
        current_sum = current_sum > 0 ? current_sum + nums[i] : nums[i];
        if (current_sum > max_sum) {
            max_sum = current_sum;
        }
    }
    return max_sum;
}

int main() {
    int nums[] = {-2, 1, -3, 4, -1, 2, 1, -5, 4};
    int size = sizeof(nums) / sizeof(nums[0]);
    printf("Max Subarray Sum: %d\n", maxSubArray(nums, size));
    return 0;
}

C++

#include <iostream>
#include <vector>
using namespace std;

int maxSubArray(vector<int>& nums) {
    int max_sum = nums[0];
    int current_sum = nums[0];

    for (int i = 1; i < nums.size(); i++) {
        current_sum = max(current_sum + nums[i], nums[i]);
        max_sum = max(max_sum, current_sum);
    }
    return max_sum;
}

int main() {
    vector<int> nums = {-2, 1, -3, 4, -1, 2, 1, -5, 4};
    cout << "Max Subarray Sum: " << maxSubArray(nums) << endl;
    return 0;
}
## Python

def max_sub_array(nums):
max_sum = current_sum = nums[0]

for num in nums[1:]:
    current_sum = max(current_sum + num, num)
    max_sum = max(max_sum, current_sum)

return max_sum

Example usage

nums = [-2, 1, -3, 4, -1, 2, 1, -5, 4]
print("Max Subarray Sum:", max_sub_array(nums))
Java
public class MaxSubArray {
public static int maxSubArray(int[] nums) {
int maxSum = nums[0];
int currentSum = nums[0];

    for (int i = 1; i < nums.length; i++) {
        currentSum = Math.max(currentSum + nums[i], nums[i]);
        maxSum = Math.max(maxSum, currentSum);
    }
    return maxSum;
}

public static void main(String[] args) {
    int[] nums = {-2, 1, -3, 4, -1, 2, 1, -5, 4};
    System.out.println("Max Subarray Sum: " + maxSubArray(nums));
}

}

Kotlin

fun maxSubArray(nums: IntArray): Int {
    var maxSum = nums[0]
    var currentSum = nums[0]

    for (i in 1 until nums.size) {
        currentSum = maxOf(currentSum + nums[i], nums[i])
        maxSum = maxOf(maxSum, currentSum)
    }
    return maxSum
}

fun main() {
    val nums = intArrayOf(-2, 1, -3, 4, -1, 2, 1, -5, 4)
    println("Max Subarray Sum: ${maxSubArray(nums)}")
}

Swift

func maxSubArray(_ nums: [Int]) -> Int {
    var maxSum = nums[0]
    var currentSum = nums[0]

    for num in nums[1...] {
        currentSum = max(currentSum + num, num)
        maxSum = max(maxSum, currentSum)
    }
    return maxSum
}

// Example usage
let nums = [-2, 1, -3, 4, -1, 2, 1, -5, 4]
print("Max Subarray Sum: \(maxSubArray(nums))")

JavaScript

function maxSubArray(nums) {
    let maxSum = nums[0];
    let currentSum = nums[0];

    for (let i = 1; i < nums.length; i++) {
        currentSum = Math.max(currentSum + nums[i], nums[i]);
        maxSum = Math.max(maxSum, currentSum);
    }
    return maxSum;
}

// Example usage
const nums = [-2, 1, -3, 4, -1, 2, 1, -5, 4];
console.log("Max Subarray Sum:", maxSubArray(nums));

Rust

fn max_sub_array(nums: Vec<i32>) -> i32 {
    let mut max_sum = nums[0];
    let mut current_sum = nums[0];

    for &num in &nums[1..] {
        current_sum = current_sum.max(current_sum + num).max(num);
        max_sum = max_sum.max(current_sum);
    }
    max_sum
}

fn main() {
    let nums = vec![-2, 1, -3, 4, -1, 2, 1, -5, 4];
    println!("Max Subarray Sum: {}", max_sub_array(nums));
}

Go

package main

import "fmt"

func maxSubArray(nums []int) int {
    maxSum := nums[0]
    currentSum := nums[0]

    for _, num := range nums[1:] {
        currentSum = max(currentSum+num, num)
        maxSum = max(maxSum, currentSum)
    }
    return maxSum
}

func max(a, b int) int {
    if a > b {
        return a
    }
    return b
}

func main() {
    nums := []int{-2, 1, -3, 4, -1, 2, 1, -5, 4}
    fmt.Println("Max Subarray Sum:", maxSubArray(nums))
}